Scalable Spin Squeezing from Critical Slowing Down in Short-Range Interacting Systems.

Area of Science:

• Quantum physics
• Condensed matter physics
• Quantum information science

Background:

• Long-range spin-spin interactions enable scalable squeezing of quantum spin ensembles, enhancing metrologically useful entanglement.
• Such squeezing is crucial for advancing quantum metrology and quantum information processing.

Purpose of the Study:

• To theoretically investigate the generation of scalable spin squeezing in 2D U(1)-symmetric systems using only short-range interactions.
• To explore the role of the Berezinskii-Kosterlitz-Thouless (BKT) critical phase in this phenomenon.

Main Methods:

• Theoretical analysis of nonequilibrium dynamics in 2D U(1)-symmetric spin systems.
• Investigation of systems initialized in a coherent spin state within the easy plane, corresponding to a thermal state in the BKT phase.
• Examination of critical slowing down and its effect on collective magnetization decay.

Main Results:

• Scalable squeezing can be achieved in 2D systems with short-range interactions, contrary to previous assumptions requiring long-range interactions.
• Nonequilibrium dynamics exhibit critical slowing down, characterized by a power-law decay of collective magnetization.
• The observed squeezing is protected by this slow decay, and its scaling directly reveals the magnetization decay exponent.

Conclusions:

• Short-range interactions in 2D U(1)-symmetric systems can generate scalable spin squeezing, expanding possibilities for quantum metrology.
• The BKT critical phase and associated critical slowing down are key mechanisms protecting the squeezing.
• These findings pave the way for creating massive entangled states in platforms like ultracold atoms and superconducting circuits.